Chemical processing of semiconductor wafers and similar substrates is often carried out with respect to relatively large batches of wafers. Typically as many as twenty or thirty wafers are simultaneously immersed in a fluid (liquid or gas) or are subjected to fluid sprays. While this is highly effective for rinsing and drying of wafers, as well as for many conventional high volume manufacturing applications, it is of questionable economy where more expensive wafers or substrates are being processed, particularly during more complex or critical processing conditions. Such large-scale batch treatments of wafers multiply potential loss due to malfunction in the processing steps. Batch handling of wafers also interrupts the normal individualized handling and development of more expensive and exotic wafers or substrates.
Individual handling and processing of wafers has also been increasingly dictated by the greater size of wafers coming into use today, as compared to earlier wafers. Where wafers once were two or three inches in diameter, some are now as large as eight inches in diameter, and wafers having a diameter of twelve inches are being used experimentally. This increase in size drastically increases the number of devices on each wafer, and correspondingly increases their potential value. Manufacturers can no longer economically risk the loss of such large numbers of devices to the many unpredictable variations encountered in batch processing operations.
The present invention was developed to minimize such economic losses by handling only a single wafer. It also adapts readily to existing single wafer production techniques common in the semiconductor industry. Furthermore, in contrast with the treatment of large batches of parallel wafers arranged in a stack, the single wafer process as described herein permits treatment of one wafer surface (by application of liquid sprays) as well as both wafer surfaces (by immersion treatment). It also readily accommodates robotic transfer of each wafer between processing units and other automated handling equipment. Indexing and rotation of each wafer can be controlled to meet precise processing requirements.
The use of individual bowls in which process steps for single wafers are conducted also allows the user to minimize the amount of fluid required for wafer. processing. The smaller fluid volume requirements permit use of fresh fluid with respect to each wafer, thereby minimizing the amount of contamination that might otherwise be encountered when recirculating fluids in larger volume systems.
The present invention pertains to components of a single wafer processing station that includes a processing base and a complementary processing head. The processing head can be portable for movement from one location to another with no restrictions on its orientation or location, or can be movably mounted relative to a common frame supporting the processing base. The details of the processing head and processing base are subject to a number of variations, depending upon the specific wafer processes to which they are directed.